Content for TS 24.186 Word version: 19.4.0

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9.3.2.2 Procedure at the IMS AS 9.3.2.2.1 IMS bootstrap data channel establishment in conjunction with MMTel session setup 9.3.2.2.1A Network-initiated IMS standalone data channel session setup 9.3.2.2.2 MMTel session modification 9.3.2.2.3 MMTel session release 9.3.2.2.4 Support of IMS standalone data channel session 9.3.2.2.5 Enforcement of 3GPP PS data off 9.3.2.2.6 Support of data channel interworking between a non-DC capable originating UE and a DC capable terminating UE 9.3.2.2.7 Handling of data channel multiplexing
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9.3.2.2 Procedure at the IMS AS p. 21

9.3.2.2.1 IMS bootstrap data channel establishment in conjunction with MMTel session setup p. 21

Based on served user service specific data which is enhanced with IMS data channel specific service details, if the IMS AS received an initial INVITE request with an SDP offer containing media description for IMS data channels, the IMS AS shall determine whether the served user is authorized to use IMS data channel.

If the served user is not authorized to use IMS data channel, then based on the operator policy the IMS AS shall determine whether to remove from the SDP offer media lines related to the IMS data channels:

If the operator policy indicates removal of media lines related to the IMS data channels, the IMS AS shall remove media lines describing the bootstrap data channel(s) i.e. "dcmap" attribute lines containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0, 10, 100 and 110, and associated with the "m=" line containing the media set to "application", the UDP port number, the proto value set to "UDP/DTLS/SCTP" and the fmt value set to "webrtc-datachannel". If there are no other "dcmap" attribute lines that contain a subprotocol parameter set to value other than "http", the IMS AS shall remove any other SDP media attribute lines associated with that m line e.g., "sctp-port", "max-message-size", "tls-id", "a=setup", "a=3gpp-qos-hint" SDP attribute lines from the received SDP offer, and send the initial INVITE request with the modified SDP offer to the S-CSCF.
If the operator policy does not indicate removal of media lines related to the IMS data channels, the IMS AS may forward media description describing the bootstrap data channel with "dcmap" attribute lines containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110, and send the initial INVITE request to the S-CSCF.

Otherwise, if the served user is authorized to use IMS data channel and the DCSF is not selected, the IMS AS shall select a DCSF and notify the DCSF about the session establishment request event, with a calling identity set to the value of the P-Asserted-Identity header field and a called identity set to the value of Request URI of the received initial INVITE request, and shall not send the initial INVITE request to the S-CSCF until receiving an acknowledgement to the corresponding notification from the DCSF.

Based on the received Media instruction set from the DCSF, the IMS AS shall select a MF and request the MF to allocate required data channel media resources. Based on the response of the reserved media resource from the MF, the IMS AS shall:

delete the bootstrap data channel media description terminated locally, i.e. local bootstrap data channel for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10);
replace the IP address represented in the attribute lines "c=" line, the UDP port number in the "m=application" line, as well as the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" within the remote bootstrap data channel media description for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110), i.e. the remote bootstrap data channel between the originating UE and terminating network, received in the SDP offer with the media resource information for the termination towards the remote network allocated on the MF if the media is anchored on the originating MF, and add "a=3gpp-bdc-used-by:" attribute line containing "bdc-used-by" parameter set to value "sender" if not present; and
generate and add the remote bootstrap data channel media description for the terminating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by:" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. remote bootstrap data channel between the originating network and the terminating UE.

Upon the reception of the successful acknowledgement to the corresponding notification from the DCSF, the IMS AS shall send the initial INVITE request with audio, video and modified data channel SDP offer to the S-CSCF towards the terminating network.

If the IMS AS received from the terminating network the UPDATE request with the SDP offer containing data channel media description for the bootstrap data channel establishment, the procedure of the IMS AS defined in clause 9.3.3.2.2.1 applies.

Upon receipt the 18x or 2xx response on the initial INVITE request including the SDP answer which includes the data channel media description, the IMS AS shall notify the DCSF about corresponding session event (session establishment progress (i.e. receiving the 183 (Session Progress) response ), session establishment alerting (i.e. receiving the 180 (Ringing) response) or session establishment success (i.e. receiving 200 (OK) response) event) and shall request the MF to update the media resource. Based on the media resource update response from the MF, the IMS AS shall:

delete the remote bootstrap data channel media description for the terminating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. the remote bootstrap data channel between terminating UE and originating network from the SDP answer;
replace the IP address represented in the "c=" line, the UDP port number in the "m=application" line, as well as the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" within the remote bootstrap data channel media description for originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and110 and "a=3gpp-bdc-used-by" attribute with "bdc-used-by" parameter set to value "sender") in the SDP answer if the media is anchored on the MF, i.e. the remote data channel for the originating UE between originating UE and terminating network, with the media resource information for the termination towards the originating UE to the terminating network allocated by the MF; and
generate and add the local bootstrap data channel media description for the originating UE (the media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and10), i.e. the local bootstrap data channel between originating UE and originating network in the SDP answer.

Upon the reception of an acknowledgement from the DCSF to the corresponding notification, the IMS AS shall include the modified SDP answer for data channel in the 18x or 2xx response and send 18x or 2xx response to S-CSCF towards the originating UE.

Upon receipt of a CANCEL request to the initial INVITE request, the IMS AS shall notify the DCSF about the session establishment cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request to the S-CSCF towards the terminating network.

Upon receipt of a 4xx, 5xx or 6xx response on the initial INVITE request from the terminating network, the IMS AS shall notify the DCSF about session establishment failure, and request the MF to release the data channel media resources.

9.3.2.2.1A Network-initiated IMS standalone data channel session setup |R19| p. 22

Upon receipt a request to setup an IMS standalone data channel session as specified in clause AG.2.2 of TS 23.228, the IMS AS shall determine whether the served user is authorized to use IMS data channel as specified in clause 9.3.2.2.1. If the served user is authorized to use data channel, the IMS AS shall select a DCSF and notify the DCSF about the external session create event. Based on the instruction from the DCSF, the IMS AS shall request the MF to allocate data channel media resources, generate the media description for the data channel as specified in clause 9.3.2.2.2.4, generate and send initial INVITE request with

SDP offer for the originating and terminating UEs as specified in clause 5.7.3 of TS 24.229;
the DC-Info header field as specified in TS 24.229 7.2.x to indicate the data channel is initiated by the DC AS.

Upon receipt of the 18x or 2xx response including SDP answer to the initial INVITE request, the IMS AS shall notify the DCSF about corresponding session event (session establishment progress (i.e. receiving the 183 (Session Progress) response ), session establishment alerting (i.e. receiving the 180 (Ringing) response) or session establishment success (i.e. receiving 200 (OK) response) event) and request the MF to update the media resource.

Upon receipt of a 4xx, 5xx or 6xx response to the initial INVITE request, the IMS AS shall notify the DCSF about session establishment failure, and request the MF to release the data channel media resources.

9.3.2.2.2 MMTel session modification p. 23

9.3.2.2.2.1 IMS bootstrap data channel establishment p. 23

If the IMS AS received from the originating UE a re-INVITE request with the SDP offer containing data channel media description for the bootstrap data channel establishment, the IMS AS shall determine whether the served user is authorized to use IMS data channel or not as specified in clause 9.3.2.2.1.

if the served user is not authorized to use IMS data channel, the procedure defined in clause 9.3.2.2.1 applies; and
if the served user is authorized to use IMS data channel, the IMS AS shall select a DCSF and notify the DCSF about the media change request event, with a calling identity set to the value of the P-Asserted-Identity header field and a called identity set to the value of Request URI of the initial INVITE request received during MMTel session establishment, if the media instruction from DCSF is:
1. to reject all the data channel medias in this request, the IMS AS shall send a 488 (Not Acceptable Here) to the originating UE if other medias are not updated; and
2. in other cases, the IMS AS shall request the MF to reserve the media resources and modify the data channel media description in the SDP offer and send the re-INVITE request as per clause 9.3.2.2.1. Upon receipt of the 183 (Session Progress) or 200 (OK) response to the re-INVITE request, the IMS AS shall send notify the DCSF about the media change success if the data channel media is accepted or media change failure if the data channel media is rejected and modify the data channel media description in the SDP answer and send the 183 (Session Progress) or 200(OK) response to S-CSCF as per clause 9.3.2.2.1. Upon receipt of a CANCEL request to the re-INVITE request, the IMS AS shall notify the DCSF about the media change cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request as per clause 9.3.2.2.1. Upon receipt of a 4xx, 5xx or 6xx response on the re-INVITE request, the IMS AS shall notify the DCSF about the media change failure and forward the response to the originating UE.

If the IMS AS received from the terminating network a re-INVITE request with the SDP offer containing data channel media description for the bootstrap data channel establishment, the procedure of the IMS AS in the terminating network on receipt of a re-INVITE request from the originating network defined in clause 9.3.3.2.2.1 applies.

9.3.2.2.2.2 IMS application data channel establishment p. 23

After the DCSF is selected, upon receipt of the re-INVITE request with an SDP offer which contains new application data channel media descriptions (the media lines with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000) along with the video, audio, and bootstrap data channel media descriptions, the IMS AS shall notify to DCSF about a media change request event. If the media instruction from the DCSF is

to reject all the data channel medias in this request, the IMS AS shall send a 488 (Not Acceptable Here) to the originating UE if other medias are not updated; and
in other cases, the IMS AS shall request the MF to allocate media resources for the application data channels based on the instruction from the DCSF if the media is anchored on the MF, and shall not send a re-INVITE request to the S-CSCF until receiving an acknowledgement to the corresponding notification from the DCSF;
based on the response on the data channel media resource update from the MF as specified in TS 29.176 and media instruction from the DCSF as specified in TS 29.175, the IMS AS shall:
1. delete the data channel media description (media line with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000 and "a=3gpp-req-app " attribute with "endpoint" parameter set to value "server") if the media instruction from the DCSF is to terminate that media;
2. delete the data channel media description if the media instruction from the DCSF is to reject the media and there are other medias to be established;
3. replace the IP address represented in the "c=" line, the UDP port number in the "m=application"in the data channel media description in the SDP offer with the media resource information for the termination towards the terminating network which is allocated by the MF if the media instruction from the DCSF is to terminate and originate the media; and also replace the DC endpoint information represented as the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" when the media proxy configuration is HTTP proxy; and
4. generate and add a data channel media description (media line with the "dcmap" attribute containing "stream-id" parameter set to values starting at 1000 and "a=3gpp-req-app " attribute with "endpoint" parameter set to value "server") by using the DC stream information provided by the DCSF in the attribute lines "a=dcmap" and "a=3gpp-req-app", DC endpoint information of the DC AS in the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup", IP address and UDP port number allocated on the termination towards to the terminating network on the MF in the "c=" line and "m=application" line when the media proxy configuration is UDP proxy, or using the DC stream information provided by the DCSF in the attribute lines "a=dcmap" and "a=3gpp-req-app", IP address, UDP port number and DC endpoint information (e.g. tlsId, sctp-port) allocated on the termination towards to the terminating network on the MF in other attribute lines above when the media proxy configuration is HTTP proxy, if the media instruction from the DCSF is to originate a new media; and
an existing application data channel media description in which a new "a=dcmap" line containing the "stream-id" parameter set to values starting at 1000 is added, the IMS AS shall notify the DCSF about media change request event, and request MF to update the media resource when receiving the media instruction from DCSF is to update the media.

Upon the reception of an acknowledgement from the DCSF to the media change request event notification, the IMS AS shall send the re-INVITE request with the modified SDP offer with the modified application data channel media description or the original application data channel media description if no media instruction received from DCSF, as well as the media description of established video, audio and bootstrap data channels.

Upon receipt of the 183 (Session Progress) or 200 (OK) response on the re-INVITE request with the SDP answer which contains media description of the requested application data channel from the terminating network:

if the application data channel is accepted, the IMS AS shall notify the DCSF about the media change success and request the MF to update the media resources. Based on the response of the MF, the IMS AS shall:
1. generate and add a data channel media description in the SDP answer by using the DC endpoint information of the DC AS provided by the DCSF in the attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" and IP address and UDP port number allocated on the termination towards to the originating UE on the MF in the "c=" and "m=application" line when the media proxy configuration is UDP proxy, or using IP address, UDP port number and DC endpoint information (e.g. tlsId, sctp-port) allocated on the termination towards to the originating UE on the MF in the attribute lines when the media proxy configuration is HTTP proxy, if the instruction from the DCSF is to terminate the media;
2. add the rejected media description and set the port number to 0 in the "m=application" line if the instruction from the DCSF is to reject the media and there are other medias to be established;
3. replace the IP address represented in the "c=" line, the UDP port number in the "m=application" in the media description in the SDP answer with the media resource information on the termination towards to the originating UE allocated by the MF, if the instruction from the DCSF is to terminate and originate the media; and also replace the DC endpoint information as attribute lines "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" when the media proxy configuration is HTTP proxy; and
4. delete the media description in the SDP answer if the instruction from the DCSF is to originate a new media;
and send the 183 (Session Progress) or 200 (OK) response with the modified SDP answer on the re-INVITE request to the S-CSCF towards to the originating UE after the receipt of an acknowledgement from the DCSF to the corresponding notification; or
if the application data channel is rejected, the IMS AS shall notify the DCSF about the media change failure event and request the MF to release the media resources. Then, the IMS AS shall send 183 (Session Progress) or 200 (OK) response to S-CSCF after the receipt of an acknowledgement from the DCSF to the corresponding notification.

Upon receipt of a CANCEL request to the re-INVITE request, the IMS AS shall notify the DCSF about the media change cancellation, request the MF to release the corresponding data channel media resources, and forward the CANCEL request as per clause 9.3.2.2.1.

Upon receipt of a 4xx, 5xx or 6xx response on the re-INVITE request from the terminating network, the IMS AS shall notify the DCSF about media change failure, request the MF to release the corresponding data channel media resources and forward the response to the originating UE.

Upon receiving the re-INVITE request from the terminating network to setup data channels and the corresponding response from the originating UE, the procedure in clause 9.3.3.2.2 applies.

9.3.2.2.2.2A Support of data channel interworking between an DC capable originatiing UE and a non-DC capable terminating UE p. 25

When the IMS AS receives an initial INVITE or the re-INVITE request with an SDP offer that contains the media description for the bootstrap data channel, the procedure in clause 9.3.2.2.1 and clause 9.3.2.2.2.1 applies. If the IMS AS receives the SIP response to the initial INVITE or the re-INVITE request in which the SDP answer indicates the remote bootstrap data channel to the terminating UE is rejected, the IMS AS may check the Contact header field of the received response. If the media feature tag "sip.video" is contained in the received Contact header field, the IMS AS may report to the DCSF about that the terminating UE supports video media. On receipt of a re-INVITE request with an SDP offer that contains media description for application data channel in which the "endpoint" parameter is set to "UE" in attribute "a=3gpp-app-req" line, the IMS AS shall follow the procedure from clause 9.3.2.2.2.2 with the following additions.

If the IMS AS, after reporting the media change request event to the DCSF as per clause 9.3.2.2.2.2, received from the:

an instruction to transform the application data channel media to video media, the IMS AS shall:
1. request the MF to allocate the video media resources as well as the data channel media resources (as specified in TS 29.176) and generate and add the SDP offer the media description for video media based on the reserved video media resource information by the MF; and
2. delete media description for the corresponding application data channel in SDP offer, or
an instruction to terminate the data channel and indicates the interworking, the IMS AS shall delete the media description for the application data channel; request the MF to allocate media resources for a P2A application data channel and notify the NEF the DC interworking required event as specified in TS 29.175.

The IMS AS shall send the re-INVITE request with the updated SDP offer to the S-CSCF towards the terminating network.

Upon receiving the 200 (OK) response with the SDP answer on the re-INVITE request, the IMS AS shall report the media change success event to the DCSF. If the instruction from the DCSF when reporting the media change request event to DCSF was:

to transform the application data channel media to video media, the IMS AS shall:
1. request the MF to associate the data channel application to the video streams as per TS 29.176;
2. delete the media description of the video media from the SDP answer; and
3. generate and add the corresponding application data channel media description in the SDP answer by using the DC endpoint information allocated on the termination towards to the originating UE on the MF with the "endpoint" parameter set to "UE" in attribute "a=3gpp-app-req" line; or
to terminate the application data channel and indicates the interworking, the IMS AS shall:
1. generate and add the corresponding application data channel media description in the SDP answer as per clause 9.3.2.2.2.2 with the "endpoint" parameter set to "server" in attribute "a=3gpp-app-req" line.

9.3.2.2.2.3 Closing application data channel p. 25

Upon receipt of the re-INVITE request with an SDP offer which contains an existing application data channel media description in which an existing "a=dcmap" is removed, the IMS AS shall notify the DCSF about media change request event, and request MF to update the media resource when receiving the media instruction from DCSF is to update the media.

Upon receipt of the re-INVITE request with an SDP offer which contains an existing application data channel media description in which the UDP port number is set to 0, the IMS AS shall notify the DCSF about media change request event, and request the MF to release the corresponding media resource when receiving the media instruction from the DCSF is to delete the media.

Upon receipt of the 200 (OK) response on the re-INVITE message with the SDP answer, the procedure in clause 9.3.2.2.2.2 applies.

Upon receiving the re-INVITE request from the terminating network to close data channels and the corresponding 200 (OK) response from the originating UE, the procedure in clause 9.3.3.2.2.3 applies.

9.3.2.2.2.4 Network-initiated data channel establishment and update p. 26

If the IMS AS received a request from the NEF or trusted AF to update an existing IMS session to add a P2A application data channel and/or bootstrap data channel as specified in TS 29.175 towards a served UE, the IMS AS shall:

determine whether the served user is authorized to use IMS data channel as specified in clause 9.3.2.2.1.
determine the request application data channel is already established based on the comparison of the application binding information included in the request from the NEF or trusted AF with the "a=3gpp-req-app" attribute line within the application data channel media descriptions included in the latest stored SDP offer/answer for this IMS session;
determine the request bootstrap data data channel is already established based on the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10 within the data channel media descriptions included in the latest stored SDP offer/answer for this IMS session; or
determine the request bootstrap data data channel and/or application data channel is already established based on the comparison of the stored media correlation IDs with the one included in the request from the NEF.

If the served user is authorized to use data channel and the requested application data channel and/or bootstrap data channel is not established, the IMS AS shall select a DCSF and notify the DCSF about the external session update event. Based on the instruction of the DCSF, the IMS AS shall request the MF to allocate data channel media resources and

generate the media description for:
1. the bootstrap data channel containing "a=dcmap" attribute line with the subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10; or
2. the P2A application data channel containing "dcmap" attribute in which "stream-id" parameter set to values starting at 1000, "a=3gpp-req-app" attribute line with "endpoint" parameter set to value "server", "c=" line and "m=application" line with the IP address and UDP port number information of termination on the MF towards to the UE, and "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" attribute lines with the information of the termination on the MF towards the UE if the media proxy configuration is HTTP, or the information of the DC AS if the media proxy configuration is UDP; and
include the DC-Info header field as specified in TS 24.229 7.2.x to indicate the data channel is initiated by the DC AS;

and generate and send a re-INVITE request to the served UE with an updated SDP offer in which the generated media description of data channel above is added.

Upon reception of the 200 (OK) response to the re-INVITE request in which:

the data channel media is accepted, the IMS AS shall notify the DCSF about the media change success event; or
the data channel media is rejected, the IMS AS shall notify the DCSF about the media change failure event.

If the IMS AS receives a request from the NEF or trusted AF to establish a P2A2P application data channel between two UEs in an existing IMS session in which the video/audio media is established, the IMS AS shall

follow the procedure above to determine the served user is authorized to use data channel and the requested application data channel is not established; and
include the DC-Info header field as specified in TS 24.229 7.2.x to indicate the data channel is initiated by the DC AS;

and generate the application data channel media descriptions and generate and send re-INVITE requests for the served UE and the remote UE.

Upon reception of the 200(OK) responses to the re-INVITE request:

if both the two UEs accept the data channel media, the IMS AS shall notify the DCSF about the media change success event;
if both the two UEs reject the data channel media, the IMS AS shall notify the DCSF about the media change failure event;
if one UE accepts the data channel media, and the other UE rejects the data channel media, the IMS AS shall send a re-INVITE request to the UE who accepts the data channel media to close the established data channel, and notify the DCSF about the media change failure.

If the IMS AS received a request from the NEF or trusted AF to update an existing IMS session to add a P2P application data channel as specified in TS 29.175, the IMS AS shall determine the served user is authorized to use data channel and the requested application data channel is not established, notify the DCSF about the external session update event. If the DCSF instructs to anchor the added application data channel on the MF of the originating network, the IMS AS shall request the MF to allocate the data channel media resource on the termination towards the served originating UE. Based on the data channel media information from the MF, the IMS AS generates an application data channel media description containing "dcmap" attribute in which "stream-id" parameter set to values starting at 1000, "a=3gpp-req-app" attribute line with "endpoint" parameter set to value "UE", "c=" line and "m=application" line with the IP address and UDP port number information and "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" attribute lines with the information of the termination on the MF towards the originating UE; and generate and send the re-INVITE request to originating UE.

Upon receiving the 200 (OK) response to the re-INVITE request including the SDP answer for the application data channel from the originating UE, the IMS AS shall request the MF to update the data channel media resources of the termination towards the originating UE and create the data channel media resources of the termination towards the terminating UE. Based on the media resources created by the MF, the IMS AS shall create an application data channel media description containing "dcmap" attribute in which "stream-id" parameter set to values starting at 1000, "a=3gpp-req-app" attribute line with "endpoint" parameter set to value "UE", "c=" line and "m=application" line with the IP address and UDP port number information and "a=tlsId", "a=sctp-port", "a=fingerprint" and "a=setup" attribute lines with the information of the termination on the MF towards the terminating network and generate and send the re-INVITE request to terminating network.

Upon receiving the 200 (OK) response to the re-INVITE request from the terminating network, the IMS AS shall update the media resources of the termination towards the terminating network. And then, the IMS AS shall send ACK to both terminating network and originating UE and notify about the media change success event.

If the served user is authorized to use data channel and the requested application data channel and/or bootstrap data channel is established, the IMS AS shall follow the requirement as specified in TS 29.175.

If the IMS AS received a request from the NEF or trusted AF to update an existing IMS session to update an application data channel and/or bootstrap data channel as specified in TS 29.175 towards a served UE, the IMS AS shall:

determine the request application data channel based on the comparison of the application binding information included in the request from the NEF or trusted AF with the "a=3gpp-req-app" attribute line within the application data channel media descriptions included in the latest stored SDP offer/answer for this IMS session;
determine the request bootstrap data data channel based on the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10 within the data channel media descriptions included in the latest stored SDP offer/answer for this IMS session; or
determine the request bootstrap data data channel and/or application data channel based on the comparison of the stored media correlation IDs with the one included in the request from the NEF; and
select a DCSF and notify the DCSF about the external session update event.

Based on the instruction of the DCSF, the IMS AS shall request the MF to update data channel media resources and update the media descriptions for the requested application data channel and/or bootstrap data channel and generate and send re-INVITE request for the served UE and also the remote UE when P2P or P2A2P application data channel is to be updated. In the re-INVITE request, the IMS AS shall include the DC-Info header field as specified in TS 24.229 7.2.x to indicate the data channel is updated by the DC AS.

If the requested application data channel and/or bootstrap data channel to update is not existed, the IMS AS shall follow the requirement as specified in TS 29.175.

9.3.2.2.2.5 Network-determined closing of bootstrap and application data channel p. 28

If the IMS AS determines to terminate the established bootstrap data channels and application data channels to the terminating UE during the session modification, the procedure defined in clause 9.3.3.2.2.4 applies.

9.3.2.2.2.6 Network-initiated data channel termination p. 28

If the IMS AS received a request from the NEF or trusted AF to update an existing IMS session to terminate an application data channel and/or bootstrap data channel towards the originating or the terminating UE as specified in clause AG.2.1 of TS 23.228, the IMS AS shall:

determine the request application data channel based on the comparison of the application binding information included in the request from the NEF or trusted AF with the "a=3gpp-req-app" attribute line within the application data channel media descriptions included in the latest stored SDP offer/answer for this IMS session;
determine the request bootstrap data data channel based on the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10 within the data channel media descriptions included in the latest stored SDP offer/answer for this IMS session; or
determine the request bootstrap data data channel and/or application data channel based on the comparison of the stored media correlation IDs with the one included in the request from the NEF; and

notify the DCSF about external session update event as specified in TS 29.175, request MF to release or update the corresponding data channel media resource and send a re-INVITE request towards the UE with the subsequent SDP offer based on the media information of the data channel required by the NEF or the trusted AF. In the SDP offer, the IMS AS shall:

set the UDP port number of the corresponding data channel media description to zero, if the required application data channel and/or bootstrap data channel is not multiplexed; or
remove the "a=dcmap" attribute line associated with the required bootstrap data channel or application data channel and also the "a=3gpp-req-app" attribute if all the related application data channels for that application are to be terminated from the corresponding multiplexed data channel media description.

In the re-INVITE request, the IMS AS shall include the DC-Info header field as specified in TS 24.229 7.2.x to indicate the data channel is terminated by the DC AS.

Upon reception of the 200 (OK) response to the re-INVITE request, the IMS AS shall notify the DCSF about the media change success event.

If the requested application data channel and/or bootstrap data channel to terminate does not existed, the IMS AS shall follow the requirement as specified in TS 29.175.

If a request is to terminate the only bootstrap data channel in an exising IMS session containing application data channels, the IMS AS shall reject the request and follow the requirement as specified in TS 29.175.

9.3.2.2.3 MMTel session release p. 28

Upon initiation or receipt of a BYE request matching an existing MMTel session with IMS data channel, the IMS AS shall notify session termination event to the DCSF and follow the call release procedure as per TS 24.229.

IMS AS shall send media resource management request to MF to release the allocated data channel media resources for this MMTel session.

Upon receipt of a request from the NEF or trusted AF to terminate an IMS standalone data channel session as specified in clause AG.2.3 of TS 23.228, the IMS AS shall request MF to release the allocated data channel media resources for this IMS standalone data channel session, send a BYE request to both the served UE and the remote network and notify session termination event to the DCSF.

9.3.2.2.4 Support of IMS standalone data channel session |R19| p. 28

9.3.2.2.4.1 General p. 28

If the IMS AS received from:

the originating UE an initial INVITE request with the SDP offer containing only data channel media description; or
the originating UE a re-INVITE request with the SDP offer in which the audio and video media is removed (i.e. the port number of the audio/video media set to 0);

the IMS AS shall determine whether the served user is authorized to use a standalone IMS data channel or not by the local configuration or the subscription data. If the user is not authorized to use IMS standalone data channel, the IMS AS shall send 401 (Unauthorized) to the originating UE to reject the session or to reject the media change request.

9.3.2.2.4.2 Standalone bootstrap data channel establishment p. 28

Upon receipt of an initial INVITE request in which:

the SDP offer only includes IMS data channel media description for the local bootstrap data channel; and
the specific "request-uri" indicating standalone data channel contained in the Request-URI,

and the IMS AS determines that the user is authorized to use standalone data channel, the IMS AS shall:

notify the DCSF about session establishment request event;
request the MF to allocate the data channel media resources as per clause 9.3.2.2.1;
return a 200 (OK) response to the initial INVITE request with the SDP answer generated as per TS 26.114 and RFC 8864] to the S-CSCF towards the originating UE; and
notify the DCSF about the session establishment success event.

9.3.2.2.4.3 Void

9.3.2.2.4.3A Subsequent standalone bootstrap data channel and application data channel establishment p. 28

Upon receipt of the initial INVITE request towards a terminating UE with the SDP offer which only includes media descriptions for bootstrap data channels and the 183 (Session Progress) response to the initial INVITE request from the terminating network, the IMS AS shall follow the procedure in clause 9.3.2.2.1 to handle the bootstrap data channel media.

Upon receipt the UPDATE request with an updated SDP offer that contains a data channel media description for the established bootstrap data channel, as well as the requested application data channel and the associated DC application binding information (provided within the "a=3gpp-req-app" SDP attribute) and the 200 (OK) response to the UPDATE request, the IMS AS shall follow the procedures upon receipt of the re-INVITE request and the response to the re-INVITE request in clause 9.3.2.2.2.2 to handle the application data channel media.

Upon receipt the 200 (OK) response to the initial INVITE request from the terminating network, the IMS AS shall notify the DCSF about the session establishment success event and forward the 200 (OK) response to the originating UE.

9.3.2.2.4.4 Combined standalone bootstrap data channel and application data channel establishment p. 29

Upon receipt the initial INVITE request towards a terminating UE with the SDP offer which includes the media description for both bootstrap data channel and application data channel and the 183 (Session Progress) response to the initial INVITE request from the terminating network, the IMS AS shall follow the procedure in clause 9.3.2.2.1 to handle the bootstrap data channel media and clause 9.3.2.2.2.2 to handle the application data channel media.

Upon receipt the UPDATE request with an updated SDP offer that contains a data channel media description for the established bootstrap data channel, as well as the requested application data channel and the associated DC application binding information (provided within the "a=3gpp-req-app" SDP attribute) and the 200 (OK) response to the UPDATE request, the IMS AS shall follow the procedure in clause 9.3.2.2.2.2 to handle the application data channel media.

9.3.2.2.5 Enforcement of 3GPP PS data off |R19| p. 30

If "Services over IMS Data Channel" is not in the list of 3GPP PS data off exempt services, upon receipt of a third-party REGISTER request containing a "+g.3gpp.ps-data-off" Contact header field parameter indicating the 3GPP PS data off status of the UE, in addition to the procedure in clause 5.7.1.26 of TS 24.229, the IMS AS serving the UE:

may notify the DCSF about the 3GPP PS data off status of the UE by session establishment request event and PS data off status change event as specified in TS 29.175, and clause X.3.2 of TS 23.228;
if the 3GPP PS data off status of the UE is changed from "inactive" to "active" and no SIP message removing all the IMS data channels in the ongoing MMTel session is received within an operator defined time, shall:
- generate a re-INVITE request including an SDP offer that contains the IMS data channel media descriptions for both bootstrap data channels and application data channels and set the UDP port number of each IMS data channel media description to zero, send to the served UE and remote network, notify the DCSF about media change request event due to the activation of the 3GPP PS data off and "Services over IMS Data Channel" is not in the list of 3GPP PS data off exempt services, and request MF to release the media resource for IMS data channels; and
- terminate the ongoing standalone IMS data channel session by applying procedures defined in 9.3.2.2.3; and
if the 3GPP PS data off status of the UE is changed from "inactive" to "active", no SIP message removing all the IMS data channels in the ongoing establishment of the MMTel session is received within an operator defined time, the IMS AS serving the UE received an initial INVITE request with IMS data channel media description(s) in the SDP offer and a final response to that initial INVITE request is not yet sent towards the served UE:
if the initial SDP offer contained only IMS data channel media description(s):
- shall send a 403 (Forbidden) response towards the served UE;
- if the initial INVITE request has been sent towards the terminating network, shall send a CANCEL request towards the terminating network;
- shall notify the DCSF about a session termination event due to the activation of the 3GPP PS data off and "Services over IMS Data Channel" is not in the list of 3GPP PS data off exempt services; and
- if the MF already allocated IMS data channel media resources, shall request the MF to release the allocated data channel media resource; or
if the initial SDP offer also contained other media description(s):
- if the IMS AS serving the UE did not yet receive the SDP answer, shall wait for reception of a SIP message with the SDP answer. Upon reception of the SDP answer, if at least one of the offered IMS data channel media descriptions is accepted (e.g., local or remote bootstrap data channel), the IMS AS serving the UE shall:
  1. modify the SDP answer by setting the UDP port number of each accepted IMS data channel media description to zero and forward the received SIP message with the modified SDP answer to the served UE; and
  2. create a new SDP offer in which the UDP port number of each accepted IMS data channel media description is set to zero and send the SDP offer within the UPDATE (or PRACK) request towards the terminating network;
- if the IMS AS serving the UE forwarded the SDP answer with accepted IMS data channel media descriptions to the served UE and there is no ongoing SDP offer/answer exchange, shall create a new SDP offer in which the UDP port number of each IMS data channel media description is set to zero and send the SDP offer within the UPDATE request towards the served UE and terminating network;
- notify the DCSF about media change request event due to the activation of the 3GPP PS data off and "Services over IMS Data Channel" is not in the list of 3GPP PS data off exempt services; and
- if the MF already allocated IMS data channel media resources, request the MF to release the allocated data channel media resource.

9.3.2.2.6 Support of data channel interworking between a non-DC capable originating UE and a DC capable terminating UE |R19| p. 31

Upon receipt of an initial INVITE request with an SDP offer containing the audio and video media description, and the IMS AS determines that the originating UE is a non-DC capable UE as specified in clause 9.2, the IMS AS may notify the NEF or the trusted AF about the interworking required event based on the subscription from them as specified in TS 29.175.

Upon receipt of an initial INVITE request with an SDP offer containing the audio and video media description from the originating UE, if the interworking required event subscribed and the IMS AS determines that the originating UE is a non-DC capable UE as specified in clause 9.2.1.2 and clause 9.2.2.2, the IMS AS shall notify the NEF or the trusted AF about the interworking required event based on the subscription from them as specified in clause AC.7.9.4 of TS 23.228 and TS 29.175.

After the final response of the initial INVITE request received, the IMS AS shall notify the NEF or the trusted AF about the IMS session establishment event based on the subscription as specified in clause AC.7.9.4 of TS 23.228 and TS 29.175.

9.3.2.2.7 Handling of data channel multiplexing |R19| p. 31

9.3.2.2.7.1 General p. 31

When the IMS AS receives from the originating UE an initial INVITE with the SDP offer containing only the multiplexed data channel media description(s), if the data channel multiplexing is not supported or not allowed, the IMS AS shall return 488 (Not Acceptable Here) response containing an SDP message body.

Upon receipt of a 488 response to the initial INVITE request with the SDP offer containing only the multiplexed data channel media description(s), the IMS AS shall notify the DCSF about session establishment failure and request the MF to modify the data channel media resources of multiplexed data channels towards the terminating network based on the media instruction from the DCSF. After the successful response from the MF, the IMS AS shall modify the SDP offer with de-multiplexed data channel media descriptions and resend the initial INVITE request towards the terminating network.

9.3.2.2.7.2 Bootstrap data channel multiplexing p. 31

When the IMS AS receives from the originating UE an initial INVITE, a re-INVITE or an UPDATE request with an SDP offer that contains a multiplexed bootstrap media description, if the data channel multiplexing is supported and allowed, the IMS AS shall select and notify the DCSF as specified in clause 9.3.2.2.1, clause 9.3.2.2.2, and clause 9.3.2.2.4.

Based on the instruction of the DCSF, the IMS AS shall select an MF supporting data channel multiplexing and request the MF to allocate data channel media resources for the multiplexed data channels. Based on the response from the MF, the IMS AS shall modify the SDP offer:

delete the local bootstrap data channel related attributes ( the "dcmap" attribute line containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10) from the received multiplexed bootstrap data channel media description and add the "a=3gpp-bdc-used-by:" attribute line containing "bdc-used-by" parameter set to value "sender" if the "dcmap" attribute line containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 presents, if the DCSF indicates the media is to be de-multiplexed and the media instruction from the DCSF is to terminate and originate the media;
generate and add the remote bootstrap data channel media description for the terminating UE (media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by:" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. remote bootstrap data channel between the originating network and the terminating UE, if the media instruction from the DCSF is to originate the media;

Upon the reception of an acknowledgement from the DCSF to the event notification, the IMS AS shall send the received SIP request with the modified SDP offer towards the terminating network.

Upon receipt of the 18x or 2xx response including SDP answer to the initial INVITE, re-INVITE or UPDATE request, the IMS AS shall notify the DCSF about corresponding session event or media change event and request the MF to update the media resource as specified in clause 9.3.2.2.1, clause 9.3.2.2.2, and clause 9.3.2.2.4. Based on the response from the MF, the IMS AS shall modify the SDP answer:

delete the remote bootstrap data channel media description for the terminating UE (media line with the "dcmap" attribute containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 100 and 110 and "a=3gpp-bdc-used-by" attribute with "bdc-used-by" parameter set to value "receiver"), i.e. the remote bootstrap data channel between the originating network and terminating UE;
add the local bootstrap data channel related attributes ( the "dcmap" attribute line containing a subprotocol parameter set to "http" and "stream-id" parameter set to values 0 and 10), and replace the IP address as well as the DC endpoint information with the media resource information allocated by the MF towards the originating UE, if the original media is multiplexed bootstrap data channel media description and the media instruction from the DCSF is to terminate and originate the media;

and send the response with the modified SDP answer towards to the originating UE.

9.3.2.2.7.3 Application data channel multiplexing p. 31

When the IMS AS receives from the originating UE an initial INVITE, re-INVITE or UPDATE request with an SDP offer that contains a multiplexed application data channel media description, if the data channel multiplexing is supported and allowed, the IMS AS shall notify the DCSF as specified in clause 9.3.2.2.2.

Based on the instruction from the DCSF, the IMS AS shall request the MF to allocate data channel media resources as specified TS 29.176.

If DCSF determines not to demultiplex the multiplexed media as specified in TS 29.175, the IMS AS shall follow the procedure of clause 9.3.2.2.2.2 to handle the application data channel media description and send the INVITE, re-INVITE or UPDATE request with the multiplexed application data channel media description in the SDP offer to the terminating network.

If the DCSF determines to demultiplex the multiplexed media, for the multiplexed media description, the IMS AS shall:

remove the parameters "adc-info" with the "adc-stream-id-endpoint" is set to "Server" in attribute "a=3gpp-req-app" line and the corresponding "a=dcmap" lines with the same "stream-id" in the multiplexed data channel media description;
if media instruction from DCSF is to originate a new media and include one existing media Id as the associated media Id in the instruction (i.e. the media identified by associated media Id is demultiplexed), generate and add a new media description for the new de-multiplexed data channel in the SDP offer; and
remove the "a=dcmap" lines and the related "a=3gpp-req-app" lines that are using separate media descriptions in bullet 2) in the original multiplexed media description.

Upon receipt of the 488 (Not Acceptable Here) response or 18x or 200 (OK) response to the INVITE, re-INVITE or UPDATE request and the multiplexed application data channel media is accepted, the IMS AS shall determine that the terminating network supports data channel multiplexing.

Upon receipt of the 488 (Not Acceptable Here) response or the 18x or 200 (OK) response in which the multiplexed application data channel media is rejected, the IMS AS shall:

notify the DCSF as specified in TS 29.175; and
de-multiplex the application data channel media description as specified in the bullet 2) and 3) above and send the INVITE, re-INVITE or UPDATE request to the terminating network again.

Upon receipt of the 18x or 200 (OK) response from the terminating network to the INVITE, re-INVITE or UPDATE request with the demultiplexed data channel media in the SDP answer, the IMS AS shall multiplex the data channel media descriptions in the SDP answer using the original multiplexed media id in the SDP offer and send the 18x or 200 (OK) response to the originating UE.